ATLANTA — The snow and sleet have stopped falling and traffic was moving again around Atlanta following a crippling storm — but transportation and rescue officials said that didn’t mean it was safe yet to drive, especially after the sun goes down.

Officials from the Georgia Department of Transportation said Wednesday night that they were concerned with sub-freezing overnight lows potentially leading to layers of black ice coating roads that might appear to be safe.

Temperatures were expected to drop to about 15 degrees overnight in the Atlanta area, according to National Weather Service forecasters. Although it was supposed to be in the high 30s Thursday, it is forecast to dip below freezing again before rising into the 50s on Friday.

“Whatever little leeway that we’ve gained with melting and slushiness is gonna refreeze,” Georgia Department of Transportation spokeswoman Karlene Barron said of local road conditions. She added that the department was especially concerned with semi-trucks jackknifing and leading to additional traffic jams.

Heeding the warnings, school districts and state and local governments stretching from northwest to coastal Georgia announced that offices and classrooms would remain closed Thursday.

A storm that dropped just inches of snow Tuesday wreaked havoc across much of the South, closing highways, grounding flights and contributing to at least a dozen deaths from traffic accidents and a mobile home fire. Yet it was Atlanta, home to major corporations and the world’s busiest airport, that was Exhibit A for how a Southern city could be sent reeling by winter weather that, in the North, might be no more than an inconvenience.

The Georgia State Patrol responded to more than 1,460 crashes between Tuesday morning and Wednesday evening, including two fatal crashes, and reported more than 175 injuries. About 1,000 arrivals and departures were canceled at Hartsfield-Jackson Atlanta International Airport, and thousands of schoolchildren either slept on the buses that tried and failed to get them home, or on cots in school gymnasiums. All were back home by Wednesday evening, officials said.

State transportation crews spent much of Wednesday rescuing stranded drivers and moving disabled and abandoned vehicles that littered the interstates, medians and shoulders. Gov. Nathan Deal said emergency workers, police, and the National Guard would help drivers Thursday to recover their cars and would provide them with fuel if necessary.

Deal and Atlanta Mayor Kasim Reed found themselves on the defensive Wednesday, acknowledging that storm preparations could have been better. But Deal also blamed federal forecasters, saying he was led to believe it wouldn’t be so bad.

However, the National Weather Service explicitly cautioned on Monday that snow-covered roads “will make travel difficult or impossible.” The agency issued a winter storm warning for metro Atlanta early Tuesday and cautioned against driving.

Deal, who is up for re-election in November, said warnings could have been posted along highways earlier, but he also fended off criticism.

“We don’t want to be accused of crying wolf. Because if we had been wrong, y’all would have all been in here saying, ‘Do you know how many millions of dollars you cost the economies of the city of Atlanta and the state of Georgia by shutting down businesses all over this city and this state?'” Deal told reporters.

The Atlanta area was crippled by an ice storm in 2011, and officials had vowed not to be caught unprepared again. But in this case, few closings or other measures were ordered ahead of time.

Among the commuters trapped in the gridlock was Jessica Troy, who described her drive home to the suburb of Smyrna as a slow-motion obstacle course on sheets of ice.

“We literally would go 5 feet and sit for two hours,” Troy said after she and a co-worker spent more than 16 hours covering 12 miles.

Nelson Kickly said he left work in Alpharetta, an Atlanta suburb, around 1 p.m. Tuesday and didn’t get home to Smyrna until 10:30 a.m. Wednesday. On a typical day, Kickly’s commute lasts about 45 minutes. He said the journey has motivated him to take a closer look at his emergency preparedness strategy.

“I had a full tank of gas but if I didn’t, I’d have been freezing cold,” he said. “I was just listening to the radio and you know, I don’t know how I didn’t go crazy.”

After daybreak, a few good Samaritans appeared, going car-to-car with bottles of water and cookies. Traffic started moving again about 8:30 a.m. Wednesday.

At Atlanta’s Deerwood Elementary School, librarian Brian Ashley, a dozen of his colleagues, and 35 children spent the night on cots set up in the gym.

The teachers and other staff members opened up the pantry in the cafeteria, making pizza and chicken nuggets accompanied by carrots and apples for dinner. Later, some police officers dropped off sandwiches, and parents living nearby brought food.

“The kids slept peacefully through the night,” Ashley said. “They knew that there were people around them that cared about them.”

However, Ashley said he was surprised officials allowed the schools to open Tuesday in the first place.

“They were forewarned about the weather, and they were ill-prepared,” he said. “If schools were canceled yesterday, we would not have had the catastrophe we did last night and today.”

Even amid the chaos, Atlanta officials insisted that downtown was open for business — at least for a huge meat- and poultry-industry exposition at the Georgia World Congress Center. Roughly 27,000 people from more than 100 countries were expected to attend between Monday and Friday.

City officials arranged for prompt scraping and ice-melting operations on roads around the center.

“Atlanta has a lot at stake with the convention business,” said Charles Olentine, the expo’s general manager. “It is mandatory that visitors to Atlanta feel welcome and attended to.”